Disposable, breath-actuated inhalers of the kind described above are for instance disclosed in WO 89/01348, U.S. Pat. No. 4,265,236 and EP-A-0404454.
EP-A-0404454 discloses a disposable, breath-actuated inhaler comprising a chamber for a pharmaceutical powder, said chamber being provided with an air inlet and with an air outlet. The air inlet and outlet are covered by a common cover. The powder is disposed loosely in the comparatively large chamber which means that the powder will not necessarily be located at that location at which the air flow is most efficient.
U.S. Pat. No. 4,265,236 discloses a tubular disposable, breath-actuated inhaler comprising a flexible tube, the ends of which normally are sealingly inserted into each other. This kind of seal will not necessarily be moisture-proof. There furthermore is a risk that some amount of the powder may fall out of the inhaler when the ends of the tube are pulled apart. WO 89/01348, in the embodiment most of interest here, discloses a tubular, disposable inhaler which is Sealed in both ends by means of twist-off caps. The. pharmaceutical powder is loosely disposed in the inhaler and, as in the other inhalers described above, there is a risk that some powder is lost when the inhaler is opened.
The objects of the invention are to provide a disposable inhaler of the kind described above in which the dose of pharmaceutical powder can be determined accurately and in which the pharmaceutical powder can be stored hermetically sealed and moisture-proof. The dose delivered by different specimens of the same inhaler should generally be constant. The inhaler finally should be easy to prepare for use and easy to use as well as being easy and cheap to manufacture.